In the food industry, lifting means are employed for loading food processing machines, for example vacuum filling machines or cutters. These lifting means are usually realized as arm lifting means or else as pole lifting means and can be attached to a machine, for example a vacuum filling machine or a cutter, or else be designed as an independent unit (“stand-alone unit”). These lifting means are designed for receiving partially standardized containers, for example mobile sausage meat trolleys (i.e. provided with rollers). In the process, the sausage meat trolley is typically transferred into the receiving unit of the lifting means such that it is securely locked against falling out and transferred by means of the lifting means, for example, upwards over the feed hopper of a vacuum filling machine. There, the sausage meat trolley is then emptied into the feed hopper. Subsequently, the sausage meat trolley is returned to its original position by means of the lifting means and removed again by the operator by releasing the locking at the lifting means. In the loading of cutters, the cutter bowl is correspondingly loaded.
The upward movement of the arm lifting means can here be designed to be superposed with the tipping movement. The upward movement of the lifting means and thus the movement of the sausage meat trolley is here effected, just as the downward movement, at a nearly constant lifting or lowering speed, apart from unintentionally acting influencing factors (e.g. vibrations).
In most cases, the lifting means comprise a hydraulic drive. In this case, the drive (i.e. for example the hydraulic pump) is operated at such high power that a maximally required lifting force (e.g. >3000 N) is provided which is greater than the maximum load corresponding to a maximum filling or a maximally admissible load (e.g. 3000 N). Even if the sausage meat trolley is only half filled, this force is provided, and the drive runs at a correspondingly high power.
For safety reasons, there is a demand on the food machines to control the downward movement of the sausage meat trolley, among other things to prevent a person located under the sausage meat trolley that moves downwards from being injured by an automatic and thus possibly uncontrolled downward movement. This safety requirement is realized in practice by a so-called “dead man's control” where the operator must continuously press a button during the lowering of the sausage meat trolley from its horizontal position on; otherwise the downward movement is stopped immediately.
The known lifting means, however, involves essential disadvantages. For example, the operator must continuously press a button during the downward movement from the horizontal line on and thus he cannot work productively. Moreover, before tipping the next sausage meat trolley into the vacuum filler, the operator must ensure that the hopper is sufficiently empty for receiving the contents of a completely filled sausage meat trolley, so that no sausage meat flows over the hopper's edge. To ensure this, one normally waits for a longer time than required. All this in practice leads to unnecessary waiting times and hinders the operating sequence.
Since for ensuring a perfect function, the maximum force of the lifting means (e.g. >3000 N) is always applied, the risk of injury to persons or the risk of damaging objects located in the motion travel of the lifting means increases as e.g. with a half filled sausage meat trolley, the power reserve (e.g. 1500 N) leads to a high risk.